TdxAutomationElementSettings.OnCalculateProperty Event

Allows you to modify individual UIA node properties depending on certain conditions.

Declaration

property OnCalculateProperty: TdxCalculateAutomationPropertyEvent read; write;

Remarks

You can handle the OnCalculateProperty event to modify individual UIA node properties depending on certain conditions (for example, you can define different node descriptions for different parent control states).

Event Occurrence

The OnCalculateProperty event occurs every time a UIA client requests an individual node property (multiple times – once per node property).

Automatic and Manual UIA Property Calculation

Automatic

Default. The OnCalculateProperty event occurs automatically for each UIA node property in supported DevExpress controls only if the dxUIACalculateAllProperties global variable is set to True.

Manual

You can set the dxUIACalculateAllProperties variable to False to disable automatic calculation for all UIA properties. In this mode, handle the OnInitializeProperties event for each required DevExpress control to specify individual UIA node properties you need to calculate.

Refer to the OnInitializeProperties event description for detailed information and code examples.

Event Parameters

The following parameters are available within an OnCalculateProperty event handler:

ASender

Provides access to the control/UI element that raised the OnCalculateProperty event.

AProperty

Provides access to the calculated UI node property.

You can use this parameter to identify the calculated UIA node property as demonstrated in the code example below.

AProperties

Provides access to the list of all UIA node properties for the parent control.

You can use AProperties.Name and AProperties.FullDescription properties to modify corresponding UIA node properties for the parent control (ASender).

Refer to the TdxCalculateAutomationPropertyEvent procedural type description for detailed information on all parameters accessible within an OnCalculateProperty event handler.

Code Example: Indicate Read-Only and Editable States

The code example in this section changes the description of an unbound single-line text editor (TcxTextEdit) in the UI Automation tree when the editor switches between read-only and editable states.

Delphi

uses
  dxUIAClasses,  // Declares all UI Automation classes
  cxEdit,  // Declares base editor classes and auxiliary types
  cxTextEdit;  // Declares the TcxTextEdit class
// ...

procedure TMyForm.cxTextEdit1PropertiesAutomationCalculateProperty(
  ASender: TObject; AProperty: TdxAutomationProperty;
  AProperties: TdxAutomationProperties);
var
  AEdit: TcxTextEdit;
begin
  AEdit := ASender as TcxTextEdit;
  // Check if the UIA node description property is requested
  if AProperty = AProperties.FullDescription then
  begin
    if AEdit.Properties.ReadOnly then
      AProperties.FullDescription.Value := 'Read-Only Mode'
    else
      AProperties.FullDescription.Value := 'Editable';
  end;
end;

C++

#include "dxUIAClasses.hpp"  // Declares all UI Automation classes
#include "cxEdit.hpp"  // Declares base editor classes and auxiliary types
#include "cxTextEdit.hpp"  // Declares the TcxTextEdit class

// Add the following linker directives to the corresponding CPP source file:
#pragma link "dxUIAClasses"  // Required to use dxUIAClasses.hpp declarations
#pragma link "cxTextEdit"  // Required to use cxTextEdit.hpp declarations
#pragma link "cxEdit" // Required to use cxEdit.hpp declarations

void __fastcall TMyForm::cxTextEdit1PropertiesAutomationCalculateProperty(
  TObject *ASender, TdxAutomationProperty *AProperty,
  TdxAutomationProperties *AProperties)
{
  TcxTextEdit *AEdit = dynamic_cast<TcxTextEdit*>(ASender);
  // Check if the UIA node description property is requested
  if(AProperty == AProperties->FullDescription)
  {
    if(AEdit->Properties->ReadOnly)
      AProperties->FullDescription->Value = "Read-Only Mode";
    else
      AProperties->FullDescription->Value = "Editable";
  }
}